Vulnerability-Lookup

GHSA-XWFF-XXVQ-7FGX

Vulnerability from github – Published: 2026-10-26 12:32 – Updated: 2026-10-26 12:32

Details

An attacker with the ability to create or modify events in a MISP instance (or a connected instance that pushes events through the guard) could craft events using different letter case in taxonomy tag names, attribute categories, or sharing-group UUIDs to bypass the configured security policies. For example, if the policy requires the 'tlp' taxonomy with only 'tlp:clear' allowed, an event tagged 'TLP:AMBER' would not be recognized as belonging to the 'tlp' taxonomy and would therefore not be checked against the allowed-tags list, resulting in the event being forwarded to feed consumers. Similarly, a blocked attribute category such as 'Person' would not match a configured block entry of 'person', allowing the attribute to pass through the filter.

The security impact is unauthorized disclosure of threat-intelligence data that the operator intended to restrict. Events carrying non-allowed TLP (Traffic Light Protocol) markings, blocked attribute categories, or blocked sharing-group associations are forwarded to downstream feed consumers in violation of the configured distribution policy. This undermines the confidentiality controls that MISP Guard is designed to enforce.

The vulnerability is trivially exploitable: the attacker only needs to alter the letter case of a tag, category, or UUID string. No authentication beyond normal MISP event-creation privileges is required, and no user interaction is needed.

Severity

7.1 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-116469"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-26T11:16:37Z",
    "severity": "HIGH"
  },
  "details": "MISP Guard, a proxy-based security filter for MISP (Malware Information Sharing Platform) feed distribution, contains a case-sensitivity flaw in multiple policy enforcement checks. The functions check_required_taxonomy_exists, check_required_taxonomy_tags_allowed, check_blocked_attribute_categories, and check_blocked_analyst_data_sharing_groups_uuids performed case-sensitive string comparisons when matching event tags, attribute categories, and sharing-group UUIDs against configured allow/block lists.\n\nAn attacker with the ability to create or modify events in a MISP instance (or a connected instance that pushes events through the guard) could craft events using different letter case in taxonomy tag names, attribute categories, or sharing-group UUIDs to bypass the configured security policies. For example, if the policy requires the \u0027tlp\u0027 taxonomy with only \u0027tlp:clear\u0027 allowed, an event tagged \u0027TLP:AMBER\u0027 would not be recognized as belonging to the \u0027tlp\u0027 taxonomy and would therefore not be checked against the allowed-tags list, resulting in the event being forwarded to feed consumers. Similarly, a blocked attribute category such as \u0027Person\u0027 would not match a configured block entry of \u0027person\u0027, allowing the attribute to pass through the filter.\n\nThe security impact is unauthorized disclosure of threat-intelligence data that the operator intended to restrict. Events carrying non-allowed TLP (Traffic Light Protocol) markings, blocked attribute categories, or blocked sharing-group associations are forwarded to downstream feed consumers in violation of the configured distribution policy. This undermines the confidentiality controls that MISP Guard is designed to enforce.\n\nThe vulnerability is trivially exploitable: the attacker only needs to alter the letter case of a tag, category, or UUID string. No authentication beyond normal MISP event-creation privileges is required, and no user interaction is needed.",
  "id": "GHSA-xwff-xxvq-7fgx",
  "modified": "2026-10-26T12:32:31Z",
  "published": "2026-10-26T12:32:31Z",
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      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116469"
    },
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}

CVE-2026-116469 (GCVE-0-2026-116469)

Vulnerability from cvelistv5 – Published: 2026-10-26 10:35 – Updated: 2026-10-26 14:35

Title

MISP Guard Case-Sensitive Policy Bypass Allows Unauthorized Feed Data Forwarding

Summary

MISP Guard, a proxy-based security filter for MISP (Malware Information Sharing Platform) feed distribution, contains a case-sensitivity flaw in multiple policy enforcement checks. The functions check_required_taxonomy_exists, check_required_taxonomy_tags_allowed, check_blocked_attribute_categories, and check_blocked_analyst_data_sharing_groups_uuids performed case-sensitive string comparisons when matching event tags, attribute categories, and sharing-group UUIDs against configured allow/block lists. An attacker with the ability to create or modify events in a MISP instance (or a connected instance that pushes events through the guard) could craft events using different letter case in taxonomy tag names, attribute categories, or sharing-group UUIDs to bypass the configured security policies. For example, if the policy requires the 'tlp' taxonomy with only 'tlp:clear' allowed, an event tagged 'TLP:AMBER' would not be recognized as belonging to the 'tlp' taxonomy and would therefore not be checked against the allowed-tags list, resulting in the event being forwarded to feed consumers. Similarly, a blocked attribute category such as 'Person' would not match a configured block entry of 'person', allowing the attribute to pass through the filter. The security impact is unauthorized disclosure of threat-intelligence data that the operator intended to restrict. Events carrying non-allowed TLP (Traffic Light Protocol) markings, blocked attribute categories, or blocked sharing-group associations are forwarded to downstream feed consumers in violation of the configured distribution policy. This undermines the confidentiality controls that MISP Guard is designed to enforce. The vulnerability is trivially exploitable: the attacker only needs to alter the letter case of a tag, category, or UUID string. No authentication beyond normal MISP event-creation privileges is required, and no user interaction is needed.

Severity

7.1 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

Supplier · CIRCL (v2.0.3)

Decision recorded 2026-10-26 10:33 UTC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-26 13:32 UTC

CWE

CWE-178 - Improper Handling of Case Sensitivity
CWE-20 - Improper Input Validation

Assigner

CIRCL CNA under the ENISA root

CNA scorecard A 90/100 over 246 records in the last 180 days details

References

1 reference

URL	Tags
https://github.com/MISP/misp-guard/commit/9868b1d…	patch

Impacted products

1 product

Vendor	Product	Version
MISP	misp-guard	Affected: 0 , ≤ 1.3 (semver) cpe:2.3:a:misp:misp-guard::::::::

Credits

Luciano Righetti Claude Opus 5.5 (1M context) Claude Opus 5.5 (1M context)

GCVE extensions

AI-generated Partially reviewed Confidence: medium Model qwen3.8:27b 1 event advisory bcp-05-x-01bcp-05-x-02bcp-05-x-03

bcp-05-x-01

AI-assisted vulnerability information annotation

GCVE-BCP-05-X-01

Whole record AI-generated Partially reviewed GNA-1

Draft vulnerability metadata was generated from a git-format patch using an Ollama-hosted language model. Human validation is required before publication.

ai-computer-assisted:llm-generatedai-computer-assisted:classification

Model	Source	Identifier
qwen3.8:27b	ollama	`qwen3.8:27b`

bcp-05-x-02

Patch-to-vulnerability generation provenance

GCVE-BCP-05-X-02

Generator: patch2vuln.py on 2026-10-26 10:33
Model: qwen3.8:27b
Input: https://github.com/MISP/misp-guard/commit/9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c.patch 26a847175a70…
Confidence: medium

Commit	Subject	Patch SHA-256
`9868b1d93fc9`	fix: [security] match categories and required taxonomies	`26a847175a70…`

Fix summary

The fix makes all policy-matching comparisons case-insensitive by applying .lower() to both the input value (tag name, attribute category, sharing-group UUID) and the configured policy value (required taxonomy prefix, allowed tags, blocked categories, blocked UUIDs) before performing the comparison. This ensures that a tag such as 'TLP:AMBER' is correctly recognized as belonging to the 'tlp' taxonomy and is checked against the allowed-tags list, and that a blocked category or UUID is matched regardless of letter case.

Patch summary

In src/mispguard.py, four comparison sites were changed: (1) check_required_taxonomy_exists now uses tag['name'].lower().startswith(required_taxonomy.lower() + ':') instead of a case-sensitive startswith; (2) check_required_taxonomy_tags_allowed applies .lower() to both the tag name and the required taxonomy prefix in the startswith check; (3) check_blocked_attribute_categories compares attribute['category'].lower() against a lowercased list of blocked categories; (4) check_blocked_analyst_data_sharing_groups_uuids compares the UUID in lowercase against a lowercased list of blocked UUIDs. Ninety-one lines of test cases were added to src/test/test_misp_guard.py covering mixed-case TLP tags in required-taxonomy checks and mixed-case blocked attribute categories.

CVSS rationale

AV:N: The MISP feed is consumed over the network (HTTP). AC:L: Exploitation requires only changing the letter case of a tag, category, or UUID string. AT:N: No log or audit tampering is needed. PR:L: The attacker needs the ability to create or modify events in a MISP instance, which typically requires a low-privilege user account or a connected instance. UI:N: No user interaction is required. VC:H: The primary impact is unauthorized disclosure of data that the operator intended to restrict (non-allowed TLP tags, blocked categories, blocked sharing groups are forwarded to feed consumers). VI:N: The data content is not modified, only improperly shared. VA:N: No availability impact. SC/SI/SA:N: No secondary system impact is evidenced.

Weakness rationale

CWE-178 The root cause is that string comparisons used to enforce security policies (taxonomy prefix matching, category blocking, UUID blocking) were case-sensitive, allowing an attacker to bypass the checks by altering letter case. CWE-178 is the most specific and accurate mapping.
CWE-20 More broadly, the guard failed to validate input against the policy in a canonical form, which is a form of improper input validation. CWE-20 is included as a secondary, broader mapping.

Attack pattern rationale

CAPEC-10 The attacker tampers with the letter case of tag names, attribute categories, or sharing-group UUIDs in MISP events to bypass the guard's policy checks. This is a form of parameter tampering where the input is modified in a way that the validation logic does not anticipate. CAPEC-10 is the closest available pattern; the uncertainty is that the tampering occurs in structured event data rather than in a traditional request parameter, but the underlying technique (modifying input to evade validation) aligns with this pattern.

Assumptions to verify

The MISP Guard is assumed to operate as a proxy filtering outbound MISP feed data; the attacker is assumed to have the ability to create or modify events in a MISP instance that feeds through the guard. The patch does not specify the exact deployment topology.
PR:L assumes that creating events in MISP requires at least a low-privilege authenticated account. If the guard is used in a context where events are pushed from a connected MISP instance without per-event authentication, PR could be None.
The CAPEC-10 mapping is the closest available pattern; the actual attack involves modifying structured JSON event fields rather than traditional HTTP parameters, so the mapping is approximate.
No specific affected or fixed version numbers are provided in the patch metadata; the version range is marked as unspecified.
The commit message references 'ID 004' as a prior related fix, suggesting this is a follow-up to an earlier incomplete case-sensitivity fix, but no further details about that prior fix are available in the patch.

Model comparison

Selected qwen3.8:27b by deterministic-consensus-v1
The selected result is closest to model consensus; this heuristic does not establish factual correctness and human review remains required.

Model	Score	Agreement	Confidence	Assumptions
`qwen3.8:27b`	7	11	medium	5

bcp-05-x-03

Vulnerability handling and disclosure timeline

GCVE-BCP-05-X-03

2026-10-26 09:25 UTC Fix developed Corrective change authored (9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c): fix: [security] match categories and required taxonomies https://github.com/MISP/misp-guard/commit/9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c.patch

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                  ],
                  "selectedModel": "qwen3.8:27b",
                  "selectionMethod": "deterministic-consensus-v1",
                  "selectionNotice": "The selected result is closest to model consensus; this heuristic does not establish factual correctness and human review remains required."
                },
                "patchSha256": "26a847175a70394b7c0feaa57f7286f41fb131fc28c4c540412e88018c749628",
                "patchSummary": "In src/mispguard.py, four comparison sites were changed: (1) check_required_taxonomy_exists now uses tag[\u0027name\u0027].lower().startswith(required_taxonomy.lower() + \u0027:\u0027) instead of a case-sensitive startswith; (2) check_required_taxonomy_tags_allowed applies .lower() to both the tag name and the required taxonomy prefix in the startswith check; (3) check_blocked_attribute_categories compares attribute[\u0027category\u0027].lower() against a lowercased list of blocked categories; (4) check_blocked_analyst_data_sharing_groups_uuids compares the UUID in lowercase against a lowercased list of blocked UUIDs. Ninety-one lines of test cases were added to src/test/test_misp_guard.py covering mixed-case TLP tags in required-taxonomy checks and mixed-case blocked attribute categories.",
                "patchTruncated": false,
                "patches": [
                  {
                    "commit": "9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c",
                    "date": "Mon, 26 Oct 2026 10:25:52 +0100",
                    "patchSha256": "26a847175a70394b7c0feaa57f7286f41fb131fc28c4c540412e88018c749628",
                    "source": "https://github.com/MISP/misp-guard/commit/9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c.patch",
                    "sourceUrl": "https://github.com/MISP/misp-guard/commit/9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c.patch",
                    "subject": "fix: [security] match categories and required taxonomies"
                  }
                ],
                "source": "https://github.com/MISP/misp-guard/commit/9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c.patch",
                "ssvc": {
                  "options": [
                    {
                      "Exploitation": "none"
                    },
                    {
                      "Automatable": "yes"
                    },
                    {
                      "Technical Impact": "partial"
                    }
                  ],
                  "role": "Supplier",
                  "timestamp": "2026-10-26T10:33:59Z",
                  "version": "2.0.3"
                },
                "subject": "fix: [security] match categories and required taxonomies",
                "weaknessRationale": [
                  {
                    "cweId": "CWE-178",
                    "rationale": "The root cause is that string comparisons used to enforce security policies (taxonomy prefix matching, category blocking, UUID blocking) were case-sensitive, allowing an attacker to bypass the checks by altering letter case. CWE-178 is the most specific and accurate mapping."
                  },
                  {
                    "cweId": "CWE-20",
                    "rationale": "More broadly, the guard failed to validate input against the policy in a canonical form, which is a form of improper input validation. CWE-20 is included as a secondary, broader mapping."
                  }
                ]
              }
            },
            "bcp-05-x-03": {
              "x_timeline": {
                "events": [
                  {
                    "description": "Corrective change authored (9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c): fix: [security] match categories and required taxonomies",
                    "id": "evt-fix-developed-1",
                    "references": [
                      "https://github.com/MISP/misp-guard/commit/9868b1d93fc9cc40cc7c69ca11c86afd825bbc1c.patch"
                    ],
                    "timestamp": "2026-10-26T09:25:52Z",
                    "type": "fix-developed"
                  }
                ]
              }
            }
          },
          "recordType": "advisory",
          "vulnId": "gcve-1-2026-20344"
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8",
    "assignerShortName": "CIRCL",
    "cveId": "CVE-2026-116469",
    "datePublished": "2026-10-26T10:35:51.992Z",
    "dateReserved": "2026-10-26T10:35:05.591Z",
    "dateUpdated": "2026-10-26T14:35:18.399Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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